Material for the powder-metallurgical production of shaped parts, in particular valve seat rings or valve guides with high resistance to wear

ABSTRACT

The invention concerns a material for the powder-metallurgical production from a powder mixture containing at least approximately 50 wt. % copper in particular of valve seat rings or valve guides with high resistance to wear and corrosion and high heat conductivity. The starting powder mixture consists of between 50 and 90 wt. % of a basic powder, containing the copper portion, and between 10 and 50 wt. % of a powdery molybdenum-containing alloy flux. The basic powder is a copper powder which is dispersion-hardened by Al 2  O 3 , has an Al 2  O 3  content of between 0.1 and 1.1 wt. %, and is produced by pulverizing a Cu--Al melt followed by heating in an oxidizing atmosphere. The invention further concerns the use of a dispersion-hardened powder of this type for the powder-metallurgical production in particular of wear and corrosion-resistant valve seat rings or valve guides with high heat conductivity. Finally, the invention concerns a method of producing such valve seat rings or valve guides.

FIELD OF THE INVENTION

The invention relates to a material for the powder-metallurgicalproduction of shaped parts with high thermal conductivity and highresistance to wear and corrosion, by pressing, sintering and, if needbe, after-compacting of a powder mixture with a copper component of atleast about 50% by weight.

Such sintered materials are required for shaped parts which are exposedto hot gases or gas mixtures, for example for the manufacture of valveseat rings and valve guides for internal combustion engines, which aresubjected to high mechanical stresses, on the one hand, andsimultaneously to the action of hot combustion gases, on the other. Suchproducts, therefore, have to be manufactured from materials which arenot only resistant to wear and corrosion, but which also have highthermal conductivity. Growing importance is attributed in thisconnection to the thermal conductivity because the temperature level onthe valves rises due to the expansion of the stoichio-metric mixturerequired for emission reasons, and because a continuing trend can beseen in the direction of more powerful engines.

BACKGROUND OF THE INVENTION

It is known to reduce the temperature difference between the head of thevalve and the head of the cylinder--into which the valve seat ring isworked--by heat transport in the valve. The shaft of the valve isprovided for said purpose with a hollow bore and is cooled. Thediameters of valve shafts have been reduced in the last few years forcost and weight reasons in such a way that it is no longer possible inmost cases to provide such shafts with a hollow bore, so that theapplication of valves drilled hollow and filled, for example withsodium, will no longer be possible in the future. Therefore, efforts arebeing made for improving the thermal conductivity of the material fromwhich the valve seat and in particular the valve seat ring ismanufactured, in order to discharge heat in this way more rapidly and tolower the temperature level for the purpose of enhancing thetribological conditions and the system both technologically and in termsof cost.

Powder-metallurgically manufactured shaped articles are known which areproduced from sintered materials based on iron with infiltrated copper.Such materials are sufficiently wear-resistant to be employed formanufacturing valve seat rings or valve guides; however, the thermalconductivity of such materials is not high enough as compared tosintered materials without copper component. For example, a sinteredmaterial is known from DE-PS 21 14 160, which consists of an iron basematerial, to which carbon and lead as well as other alloying componentsare added. Valve seat rings produced from said material do have adequateresistance to heat and wear; however, their thermal conductivity isinadequate for solving the problem here on hand especially within theregion of the outlet of a modern internal combustion engine.

A sintered material for the powder-metallurgical production of valveseat rinds is known from PCT-EP 89/01343. Such valve seat rings areexpected to have increased thermal conductivity combined with highresistance to wear. The sintered material consists of a basic metalpowder with a copper component of about 70% to 100% by weight, as wellas with an alloying component. The latter may consist of, for example 1to 3% by weight cobalt or a highly alloyed additional metal powder addedto the basic metal powder as a hard phase, the proportion of which thencomes to 30% by weight at the most.

Tests carried out with such a material have shown that the material hasa resistance to wear which is not sufficient for the manufacture ofvalve seat rings, and particularly not for the outlet region of internalcombustion engines. This has to be attributed to the fact that eventhough it was possible to increase the hardness of the material throughsolidification of the matrix by incorporating hard substances with amaximum particle size of 150 μm, and thus to increase the resistance ofthe valve seat ring to wear, on the one hand, the counter body showedstronger wear due to the relatively large and sharp-edged incorporatedparticles, on the other. Therefore, the wear on the valve seat ring waslow, whereas the overall wear, which is important to the lastingfunctioning of the system, became worse.

SUMMARY OF THE INVENTION

The invention is based on the problem of creating a sintered materialfor the powder-metallurgical manufacture particularly of valve seatrings or valve guides, such sintered material having very highresistance to wear and at the same time a significantly high thermalconductivity as compared to known sintered materials employed for saidpurpose.

Based on a material for the powder-metallurgical manufacture of shapedparts with high resistance to wear and corrosion in particular for theproduction of valve seat rings or valve guides for internal combustionengines, by pressing, sintering and, if need be, after-compacting of astarting powder mixture with a copper component of at least about 50% byweight, the invention consists in that the starting powder mixtureconsists of a basic powder in an amount of from 50% to 90% by weight,such basic powder containing the Cu-component, and a powdery alloyingaddition in an amount of from 10% to 50% by weight, said alloyingaddition containing molybdenum; and in that the basic powder is adispersion-hardened copper powder. The dispersion-hardened copper powderis preferably hardened by Al₂ O₃ and contains from 0.1% to 1.1% byweight Al₂ O₃ and less than 0.5% by weight impurities, and it isproduced by pulverizing a Cu--Al-melt and subsequent heating in anoxidizing atmosphere for selectively oxidizing the aluminum.

The invention is based on the surprising finding that the application ofa Cu--Al₂ O₃ -powder that has been dispersion-hardened in a definedmanner preferably by means of Al₂ O₃ for the powder-metallurgicalproduction of shaped articles will lead to products which have highresistance to wear and corrosion, on the one hand, as well as highthermal conductivity on the other, so that such products areparticularly suitable for the manufacture of valve seat rings or valveguides.

Only Cu-powders dispersion-hardened with Al₂ O₃ are suitable for thepresent application purposes, such powders having been produced, forexample by the process known from U.S. Pat. No. 3,779,714 or DE-PS 23 55122, i.e., by inner oxidation and subsequent heating of Cu--Al-powderproduced by pulverizing a Cu--Al-melt, in an oxidizing atmosphere,whereas dispersion-hardened metal powders produced by another processaccording to GB-A-2 083 500, where inner odidation is expressivelyexcluded, are unsuitable. Applicant attributes this to the fact that ina Cu--Al₂ O₃ -powder produced by means of inner oxidation, the spacingbetween the dispersed Al₂ O₃ -particles in the copper matrix is in theorder of magnitude of 3 to 12 nm, whereas it amounts to approximately 40μm in the powder produced without inner oxidation. Nothing is stated inthe documents cited above about the application of dispersion-hardenedmetals as defined by the invention, i.e., as a basic powder for thepowder-metallurgical manufacture of shaped articles, in particular valveseat rings or valve guides.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 discloses the relationship between conductivity and valve seatrings based on Fe with and without copper infiltration.

FIG. 2 discloses engine results based on the characteristics of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

According to a preferred embodiment of the invention, provision is madethat the alloying addition consists of a powdery, preferablywater-atomized intermetallic hard phase consisting of 28% to 32%,preferably 30% by weight molybdenum, 9% to 11%, preferably 10% by weightchromium, 2.5% to 3.5%, preferably 3% by weight silicon, the balancecobalt, whereby the intermetallic phase is present in the powder mixturein an amount of about 10% by weight, and the basic powder is presenttherein in and amount of about 90% by weight.

According to another embodiment of the invention, the intermetallicphase consists of 28% to 32%, preferably 30% by weight molybdenum, 9% to11%, preferably 10% by weight chromium, 2.5% to 3.5%, preferably 3% byweight silicon, the balance iron, whereby the intermetallic phase ispresent in the powder mixture in an amount of about 10% by weight, andthe basic powder in an amount of about 90% by weight.

According to the invention, the alloying addition may consist also of ahard phase consisting of a high-speed steel powder consisting of about6% by weight tungsten, about 5% by weight molybdenum, about 2% by weightvanadium, about 4% by weight chromium, the balance iron, whereby thehard phase is present in the powder mixture in an amount of up to about30% by weight, and the basic powder in an amount of about 70% or higher.

Furthermore, the alloying addition may also consist of a hard phaseconsisting of an Mo--P--C-powder consisting of about 11% by weightmolybdenum, about 0.6% by weight phosphorus, about 1.2% by weightcarbon, the balance iron, whereby the hard phase and the basic powdereach are present in the powder mixture in an amount of approximately 50%by weight.

Furthermore, the object of the invention is a material consisting of astarting powder mixture consisting of about 80% by weight basic powder,about 10% by weight molybdenum powder, and about 10% by weight copperpowder, or about 79% by weight basic powder, about 10% by weightmolybdenum powder, about 10% by weight copper powder, and about 1% byweight powdery molybdenum troxide.

Furthermore, according to the invention, the basic powder additionallycontains molybdenum disulfide (MoS₂) and/or manganese sulfide (MnS)and/or tungsten disulfide (WS₂) and/or calcium fluoride (CaF₂) and/ortellurium (Te) and/or calcium carbonate (CaCO₃), in a total amount of atleast 1% by weight up to maximally 3% by weight based on the amount ofbasic powder.

Furthermore, the object of the invention is a process for thepowder-metallurgical production of shaped parts with high resistance towear and corrosion and with high thermal conductivity, in particular forthe manufacture of valve seat rings or valve guides for internalcombustion engines, in which process a starting powder mixture havingone of the compositions specified above is mixed with about 0.3% byweight or an agent facilitating pressing, e.g. wax, shaped, and pressedinto a shaped part with a density around about 8.0 g/cm³, andsubsequently subjected to sintering under protective gas, such sinteringpreferably being carried out in a protective gas atmosphere consistingof about 80% by weight nitrogen and about 20% by weight hydrogen, for aduration of about 45 minutes at a temperature of about 1,040° C. If needbe, the sintered shaped part can be subjected to after-compacting to adensity of about 8.8 g/cm³.

According to an alternative embodiment of the invention, provision ismade that the starting powder according to claim 1 contains one or aplurality of the following substances or substance mixtures:

    ______________________________________                                        (a) 5 to 30%  by weight tool steel type M35 or type T15,                                              Ni--Cr--Si--Fe--B--Cu--Mo;                            (b) 5 to 10%  by weight W, Mo, Nb, WC, TiC, B.sub.4 C, TiN, c-EN,                                     TiB.sub.2 ;                                           (c) 0.5 to 5% by weight Ti, Cr, Zr, Cr + Zr, Be, Ni + P.                      ______________________________________                                    

The materials of group (a) alloy with the copper matrix of thedispersion-hardened copper in that such additions diffuse into thecopper and thereby significantly reduce the electric and the thermalconductivity. The proportionate amount should not exceed 5% to 20% byweight, typically 10% by weight, in order to maintain the thermalconductivity at above 100 W/m·k.

The materials Of group (b) do not alloy with the copper matrix andtherefore do not have any notable influence on the thermal conductivity.Said materials are rather costly, however, it was found that aproportion of 5% to 10% by weight will suffice.

The additions of group (c) cause separation of the intermetalliccomponents and in this way superpose the hardening effect in addition tothe hardening caused by the Al₂ O₃ -particles in the dispersion-hardenedcopper. While the aluminum oxide-particles cause effective hardening ofthe copper matrix at elevated temperatures (>500° C.), the separationphases cause more effective hardening in the mean temperature range(200° to 500° C.), whereby the latter represents the typical operatingtemperatures to which valve seat rings are exposed to. The higher hothardness generally leads to higher resistance to wear.

The wear of the valve seat rings is caused also by the addition of solidlubricants such as graphite, MoS₂, MnS, h-BN, CaF₂ and the like, as wellas by metal additions such as Mo, Co, W or the like, which, at theoperating temperatures, form oxide skins which have a lubricatingeffect.

Owing to the fact that the starting powder contains one or several ofthe following materials,

5 to 20% Zn, 0.1 to 5% by weight of one of the elements Al, Be, Si, Mg,Sn,

the resistance to oxidation, i.e., the resistance to corrosion duringoperation is significantly increased. Zn is the preferred alloyingcomponent in view of the fact that the thermal conductivity is to bereduced as little as possible. An addition of 5 to 30% by weight is notcritical in this regard.

The starting powder preferably contains one or a plurality of thefollowing powdery substances with an irregular particle shape:

5 to 25% by weight Cu with high green strength; Electrolyte-Cu;oxide-reducing Cu; Mo or the like.

Owing to the fact that the dispersion-hardened copper used has round,smooth particles, the unsintered green particles of said material haveonly low strength. The green strength can be significantly increased byadding the components specified above. The "Cu with high green strength"is a powder with fiber-like, long thin particles which, when pressedtogether, entwine each other, effecting in this way high strength of thegreen body. The thermal conductivity is not affected by adding pure Cu,so that 5% to 25% by weight can be added, with the preferred range being10% to 15% by weight.

The workability, in particular the machine ability ofdispersion-hardened copper is enhanced by adding one or a plurality ofthe following substances:

    ______________________________________                                        (a) 0.2 to 2%                                                                              by weight chemical elements such as C (graphite),                                       Te, Se;                                                (b) 0.5 to 5%                                                                              by weight sulfides such as MoS.sub.2, MnS, etc.;                 (c) 0.5 to 5%                                                                              by weight oxides such as MoO.sub.3, WO.sub.3, Co.sub.3                                  O.sub.4 etc.,                                          (d) 0.5 to 5%                                                                              by weight compounds such as hexagonal BN, CaF.sub.2.             ______________________________________                                    

The radial ultimate breaking strength of the valve seat rings, which isrequired especially when the ring is pressed into the cylinder head, isincreased by adding one or several of the following substances:

    ______________________________________                                        (a)   5 to 20%  by weight Zn, 0.1-5% by wt. Al or Sn, etc;                    (b)   5 to 30%  by weight tool steel type M35 or type T15,                                              Ni--Cr--Si--Fe, B--Cu--Mo.                          ______________________________________                                    

By combining the above alloying additions accordingly it is possible tooptimally adjust the starting powder mixture in view of the propertiesrequired for the valve seat ring in the given case.

The principal advantage in view of the manufacture of valve seat ringslies with all aforementioned starting powder mixtures as defined by theinvention in the fact that the thermal conductivity is particularlyhigh, i.e., amounting to at least 100 W/m·k.

EXEMPLIFIED EMBODIMENTS Example 1

A Cu--Al₂ O₃ -powder dispersion-hardened by means of inner oxidation,with a content of 0.5% by weight Al₂ O₃, was mixed with 0.3% by weightof a commonly used agent facilitating pressing, and pressed at apressing pressure of 800 MN/mm² to shape valve seat rings with thedimensions 36.6×30.1×9 millimeters. The blanks, which had a pressingdensity of 8.4 g/cm³, were subsequently sintered for 45 minutes at atemperature of 1,040° C. in a protective gas atmosphere consisting of80% N₂ and 20% hydrogen. The sintering density came to 8.4 g/cm³. Thesintered rings were subsequently subjected to after-compacting to adensity of 8.8 g/cm³ at a pressure of 1,600 MN/mm².

Table 1 shows the measured density and hardness values, and table 2 thevalues of thermal conductivity determined according to the laser flashmethod.

                  TABLE 1                                                         ______________________________________                                        Process Steps                                                                            Density [g/cm.sup.3 ]                                                                      Hardness HB                                           ______________________________________                                        Pressing   8.41         --                                                    Sintering  8.41         89 - 99 - X =                                                                               93                                      After-compacting                                                                         8.83         111 - 129 - X =                                                                            121                                      ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Temperature [° C.]                                                                   Thermal Conductivity [W/m · k]                         ______________________________________                                        RT            276                                                             100           300                                                             200           310                                                             300           308                                                             400           311                                                             500           307                                                             600           313                                                             700           311                                                             ______________________________________                                    

Example 2

90% by weight of a dispersion-hardened Cu--Al₂ O₃ -powder produced bymeans of inner oxidizing with an Al₂ O₃ -content of 0.5% by wt. wasmixed with 10% by weight of a water-atomized, powdery intermetallic hardphase, and 0.3% by wt. of a commonly used agent employed forfacilitating pressing. The intermetallic hard phase consisted of 60% byweight cobalt, 30% by weight molybdenum, 10% by weight chromium, and 3%by weight silicon. The powder mixture was pressed in molds into valveseat rings at a molding pressure of 800 MN/mm², the rings were sized36.6×30.1×9 mm. The green blanks had a pressing density of 8.2 g/cm³.The rings were subsequently sintered for 45 minutes at a temperature of1,040° C. in a protective gas atmosphere consisting of 80% N₂ and 20%H₂. The sintering density came to 8.2 g/cm³. After-compacting to adensity of 8.7 g/cm³ was carried out at a pressure of 1,600 MN/mm².

Table 3 below shows the density and hardness values, and table 4 thevalues of thermal conductivity determined according to the laser flashmethod.

                  TABLE 3                                                         ______________________________________                                        Process Steps                                                                            Density [g/cm.sup.3 ]                                                                      Hardness HB                                           ______________________________________                                        Pressing   8.20         --                                                    Sintering  8.20         88 - 101 - X =                                                                              94                                      After-compacting                                                                         8.73         124 - 142 - X =                                                                            133                                      ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Temperature [° C.]                                                                   Thermal Conductivity [W/m · k]                         ______________________________________                                        RT             95                                                             100           102                                                             200           117                                                             300           129                                                             400           139                                                             500           150                                                             600           157                                                             700           155                                                             ______________________________________                                    

The valve seat rings produced according to examples 1 and 2 exhibited anunexpected improvement with respect to thermal conductivity versuscommercially available valve seat rings based on Fe with and withoutcopper infiltration.

This is shown by FIG. 1. Curve 1 shows the values of thermalconductivity of a valve seat ring according to example 1. Curve 2 showsthe values of a ring according to example 2; curve 3 the values of avalve seat ring based on Fe with copper infiltration; and curve 4 thevalues of a commercially available valve seat ring of the ApplicantFirm.

The rings produced according to example 1 showed a hardness permittingtheir application in the inlet region of an internal combustion engine,whereas the valve seat rings according to example 2 can be used in theoutlet region, where they exhibit excellent running behavior. This wasdetermined in tests; the conditions of these tests are summarized intable 5 below.

                  TABLE 5                                                         ______________________________________                                        Test duration:     125 hours                                                  Number of cylinders:                                                                             4                                                          Number of values/cylinder:                                                                       4                                                          Displacement:      1998 cm.sup.3                                              Output:            100 kW at 5500 rpm                                         Torque:            190 Nm at 4000 rpm                                         Fuel:              Super lead-free - ROZ 95                                   Engine oil:        Shell Super 3 - 10 W 40                                    Valve disk, inlet: uncoated                                                   Valve disk, outlet:                                                                              Stellite-armored                                           ______________________________________                                    

The results of the engine test are summarized in table 6 and graphicallyshown in FIG. 2. The sink-in depth is the sum of the wear of the valveand the valve seat ring. The valve seat sing as defined by the inventionaccording to example 2 was compared with the material Como 12 of theApplicant Firm, which is a product manufactured in series and usedwidely.

                  TABLE 6                                                         ______________________________________                                                           Sink-in depth [mm]                                         ______________________________________                                        Outlet                                                                        (b)    Cu-Al.sub.2 O.sub.3 with 10%                                                                    0                                                           intermetallic hard phase                                                                        0.02                                                 Series-produced material                                                                           0.02                                                     COMO 12              0.07                                                                          0.04                                                                          0                                                        ______________________________________                                    

The table shows that the sink-in depth of the valve seat ring as definedby the invention is lower than the one of a commercially available valveseat ring, combined with significantly increased thermal conductivity.

We claim:
 1. A material for the powder-metallurgical production ofshaped parts with high resistance to wear and corrosion and high thermalconductivity, in particular for the manufacture of valve seat rings orvalve guides for internal combustion engines, by pressing, sinteringafter-compacting of a starting powder mixture with a copper component ofat least about 50% by weight, characterized in that the starting powdermixture consists of a basic powder in an amount of from 50% to 90% byweight, said powder containing the Cu-component, and a powderymolybdenum-containing alloying addition in an amount of from 10% to 50%by weight; and that the basic powder is a dispersion-hardened copperpowder.
 2. The material according to claim 1, characterized in that thedispersion-hardened copper powder is hardened by from 0.1% to 1.1% byweight Al₂ O₃ ; that it contains less than 0.5% by weight impurities;and that it is produced by atomizing a Cu--Al-melt followed by heatingin an oxidizing atmosphere for the selective oxidation of the aluminum.3. The material according to claim 1, characterized in that the alloyingaddition consists of a powdery, preferably water-atomized intermetallichard phase.
 4. The material according to claim 1, characterized in thatthe intermetallic hard phase has the following composition:28% to 32%,preferably 30% by weight molybdenum; 9% to 11%, preferably 10% by weightchromium; 2.5% to 3.5%, preferably 3% by weight silicon; the balancecobalt.
 5. The material according to claim 4, characterized in that theintermetallic hard phase is present in the powder mixture in an amountof about 10% by weight, and the basic powder is present therein in anamount of about 90% by weight.
 6. The material according to claim 1,characterized in that the intermetallic hard phase has the followingcomposition:28% to 32%, preferably 30% by weight molybdenum; 9% to 11%,preferably 10% by weight chromium; 2.5% to 3.5%, preferably 3% by weightsilicon; the balance iron.
 7. The material according to claim 6,characterized in that the intermetallic phase is present in the powdermixture in an amount of about 10% by weight, and the basic powder ispresent therein in an amount of about 90% by weight.
 8. The materialaccording to claim 1, characterized in that the alloying additionconsists of a hard phase consisting of a high-speed steel powder (AISItype M2; DIN S-6-5-2) with the following composition:About 6% by weighttungsten; about 5% by weight molybdenum; about 2% by weight vanadium;about 4% by weight chromium, the balance iron.
 9. The material accordingto claim 8, characterized in that the hard phase is present in thepowder mixture in an amount of up to 30% by weight, and the basic powderis present therein in an amount of about 70% by weight or higher. 10.The material according to claim 1, characterized in that the alloyingaddition consists of a hard phase consisting of an Mo--P--C-powder withthe following composition:About 11% by weight molybdenum; about 0.6% byweight phosphorus; about 1.2% by weight carbon; the balance iron. 11.The material according to claim 10, characterized in that the hard phaseand the basic powder each are present in the powder mixture in an amountof about 50% by weight.
 12. The material according to claim 1,characterized by the following composition of the starting powdermixture:About 80% by weight basic powder; about 10% by weight molybdenumpowder; about 10% by weight copper powder.
 13. The material according toclaim 1, characterized by the following composition of the startingpowder mixture:About 79% by weight basic powder; about 10% by weightmolebdenum powder; about 10% by weight copper powder; and about 1% byweight molybdenum trioyide.
 14. The material according to claim 1,characterized in that the basic powder additionally contains molybdenumdisulfide (MoS₂) and/or manganese sulfide (MnS) and/or tungstendisulfide (WS₂) and/or calcium fluoride (CaF₂) and/or tellurium (Te)and/or calcium carbonate (CaCO₃) in a total amount of at least 1% byweight up to maximally 3% by weight based on the amount of basic powder.15. A method for the powder-metallurgical production of shaped partswith high resistance to wear and corrosion and high thermalconductivity, in particular for the manufacture of valve seat rings orvalve guides for internal combustion engines, characterized in that astarting powder mixture according to one of the preceding claims ismixed with about 0.3% by weight of an agent facilitating pressing, forexample wax, shaped and pressed to a shaped part with a density of about8.0 g/cm³ and subsequently subjected to sintering under protective gas.16. The method according to claim 15, characterized in that sintering itcarried out in a protective gas atmosphere consisting of about 80% byweight nitrogen and about 20% by weight hydrogen for a duration of about45 minutes at a temperature of about 1,040° C.
 17. The method accordingto claim 15, characterized in that the sintered shaped article issubjected to after-compacting t6 a density of about 8.8 g/cm³.
 18. Acomposition comprising a Cu--Al₂ O₃ -powder with an Al₂ O₃ -contentbetween 0.3 and 1.1% by weight dispersion-hardened by means of Al₂ O₃and produced by atomizing a Cu--Al-melt and subsequent heating in anoxidizing atmosphere, for the powder-metallurgical manufacture of wear-and corrosion-resistant shaped parts with high thermal conductivity, inparticular for the manufacture of valve seat rings or valve guides. 19.The materials according to claim 1, characterized in that the startingpowder mixture contains one or several of the following materials ormaterial mixtures:(a) 5% to 30% by weight tool steel type M35 or typeT15, Ni--Cr--Si--Fe--B--Cu--Mo; (b) 5% to 10% by weight W, Mo, Nb, WC,TiC, B₄ C, TiN, c-BN, TiB₂ ; (c) 0.5% to 5% by weight Ti, Cr, Zr, Cr+Zr,Be, Ni+P.
 20. The materials according to claim 1, characterized in thatthe starting powder mixture contains one or several of the followingmaterials:5% to 10% by weight Co, W.
 21. The material according to claim1, characterized in that the starting powder mixture contains one orseveral of the following materials:5% to 20% by weight Zn, 0.1% to 5% byweight of one of the elements Al, Be, Si, Mg, Sn.
 22. The materialaccording to claim 1, characterized in that the starting powder mixturecontains one or several of the following powdery materials with anirregular particle shape:5% to 25% by weight Cu with high greenstrength, electrolyte-Cu, oxide-reduced Cu, Mo.
 23. The materialaccording to claim 1, characterized in that the starting powder mixturecontains one or several of the materials specified in (a) to (d):

    ______________________________________                                        (a) 0.2% to 2%                                                                              by weight                                                                              chemical elements such as C (graphite),                                       Te, Se;                                                (b) 0.5% to 5%                                                                              by weight                                                                              sulfides such as MoS.sub.2, MnS, etc.;                 (c) 0.5% to 5%                                                                              by weight                                                                              oxides such as MoO.sub.3, WO.sub.3, Co.sub.3                                  O.sub.4, etc.;                                         (d) 0.5% to 5%                                                                              by weight                                                                              compounds such as hexagonal BN, CaF.sub.2.             ______________________________________                                    


24. The material according to claim 1, characterized in that thestarting powder mixture contains one or several of the followingmaterials:

    ______________________________________                                        (a) 5% to 20% by weight Zn; 0.1 to 5% by wt. Al or Sn, etc.;                  (b) 5% to 30% by weight tool steel type M35 or type T15,                                              Ni--Cr--Si--Fe--B--Cu--Mo.                            ______________________________________                                    


25. The material according to claim 1 and, characterized in that thestarting powder mixture contains combinations of the materials ormaterial mixtures.
 26. Application of a material according to claim 1and for the manufacture of a valve seat ring or valve guides having athermal conductivity of at least 100 W/m·k.